(1) Field of the Invention
The present invention relates to a detection method and apparatus for a wiring pattern using a triangulation method in which a light is obliquely incident on an object and a measurement is made from another oblique direction, to detect a height of the wiring pattern, and more particularly, it relates to a detection method and apparatus for a wiring pattern for expanding a wiring pattern height measurable domain and by which a pattern having a height between an upper allowable limit and a lower allowable limit thereof can be accurately determined.
(2) Description of the Related Art
Generally, a wiring pattern on a printed circuit board has a predetermined pattern width and height (thickness) conforming to a required design, but sometimes a failure occurs such as a pattern disconnection, partial defect and the like due to various factors in the production processes. Among the failures occurring in a wiring pattern, for example, a copper film having a three dimensional configuration, are the defects of an abnormal width and an insufficient thickness of the copper film. With regard to the thickness defect, upper and lower limits thereof are defined, and the thickness of the wiring pattern must be within these allowable limits. Conventionally, however, the pattern is examined only to a narrow extent, to determine whether it is within a predetermined height.
Accordingly, in the conventional method of detection of a wiring pattern, since the thickness of the wiring pattern is only determined to be higher or lower in comparison with a threshold value (a predetermined height), a problem arises in that the conventional method cannot accurately determine an area within the allowable extent of the upper and lower limits of the wiring pattern thickness.
Further, in the conventional method of detection of a wiring pattern, when the slice level value is set as a threshold value, since the slice level voltage is determined by adding a constant voltage to the voltage corresponding to the surface of a substrate on which the wiring pattern is formed, in the case of a curved substrate, for example, the relationship between the slice level voltage and the detection signal is often unsuitable.